Print-receiving elements for diffusion transfer reversal processes and film assemblies embodying said elements



Apnl 16, 1957 E. H. LAND 2,789,054

PRINT-RECEIVING ELEMENTS FOR DIFFUSION TRANSFER REVERSAL PROCESSES AND FILM ASSEMBLIES EMBODYING SAID ELEMENTS Filed Dec. 29, 1953 I2. Supper! FIG. I

ii i

. I on'kainer FIG. 2

' INVENTORY.

.ATTQRNEYS PRINT RECEIVING ELEMENTS FOR DIFFUSION TRANSFER REVERSAL PROCESSES AND FILM ASSEMBLIES EMBODYING SAID ELEMENTS 'l and, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Massqa corporation of Delaware Application December 29, 1953, Serial No. 401,022

' 5 Claims. c1. 9629) This invention relates to photographic products and more particularly to print-receiving elements useful in silver diffusion transfer reversal processes and to film structures embodying such elements.

Transfer processes involving the development of a latent image in a silver halide emulsion and the transfer ofcomponents from said emulsion to another layer to effect the formation of a print of said latent image in saidother layer,- are now well known. A species of this type of processing involves the transfer by diffusion of silver from the silver halide emulsion in the form of a soluble silver complex and the reduction of the silver of the complex in or on a suitable print-receiving element. Certain of these processes have been disclosed in my Patent No. 2,543,l8l,issued February 27, 1951 for Photographic Product Comprising a Rupturable Container Carrying a Photographic Processing Liquid, and my Patent No. 2,647,056, issued July 28, 1953 for One Step Photographic Transfer Process. Prints of superior pictorial quality have been obtained by using a printreceiving element equipped with a print-receiving stratum which is relatively thin and which comprises an inert matrix, preferably of colloidal particles of a siliceous material, and a silver precipitating agent distributed throughout said matrix. Such print-receiving elements preferably comprise a relatively water-impervious subcoat for the silver precipitating stratum and examples of this type 'of reception material have been described in my copending application Serial No. 234,622, filed June 30, 1951 for Photographic Silver Halide Transfer Process and the Print-Receiving Products Useful in Connection Therewith.

To protect prints formed upon print-receiving elementsof-theforegoing type, it hasbeen proposed to wash the surface of the print to remove therefrom the relatively minute quantities of reagents which might otherwise adversely aflect the quality of the print and to simultaneously deposit on said surface a layer of film-forming protective material which solidifies thereon to-form'a continuous protective film. Thus, the printreceiving stratum in which thesilver image is formed becomes sandwiched between its relatively water-impervious subcoat and this protective film. Methods for applying such protective films and preferred compositions for this purpose are disclosed in the copending applicationsof Edwin H. Land, Serial No. 302,746, filed August i, 1952 for Method of Improving the Stablilization of Finished Photographic Prints by Applying a Liquid Composition Thereto, and the Product of Said Method, and of Edwin H. Land, Elkan R. Blout and Howard C. Haas, Serial No. 359,438, filed June 3, 1953 for Process of Washing and Protecting Photographic Silver Images, Photographic Materials Usable Therein and Photographic Products Thereof.

It'has now been determined that, despite these special precautions, elemental sulfur under certain conditions, as-where'the print is;brought into contact with such materials as sulfur-containing cardboards, has the capacity of 2 ,789,054- Patented Apr. 16; 1957 'This' migration appears to give elemental sulfur direct access to the silver in said print-receiving stratum. It has been found, for example, that minute quantities of plasticizer in a relatively remote part ofIa film assembly embodying a print-receiving element of the foregoing type will migrate during storage of that assembly into said element and, although having no immediate visible effect on a print formed on said element after such storage, will render the silver in the penetrated portion of said element subject to subsequent attack by elemental sulfur.

It is accordingly one object of the present invention to provide as a subcoat for the silver precipitating stratum of a print-receiving element one or more films of material which are capable of preventing the penetration of liquids other than water through the underside of said printreceiving element to the silver precipitating stratum so that by providing a print formed in such an element with a protective outer coating of a similarly impenetrable material it becomes possible to substantially completely exclude elemental sulfur from the silver of the print.

These and other objects of the present invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed disclosure taken in connection with the accompanying drawing wherein:

Figure l is a diagrammatic, enlarged, sectional View illustrating one type of print-receiving element embodying the present invention, the thicknesses of some of the layers of the print-receiving element being exaggerated and not necessarily in correct relative proportion, and

Fig. 2 is a similar view of a composite film unit or assembly embodying a print-receiving element of the foregoing type.

The print-receiving elements of the present invention are particularly useful in processes of the type wherein a positive print is obtained in a single step by suitably treating a silver halide emulsion containing a latent image with a uniformly applied layer of processing liquid. The processing liquid is preferably in a viscous condition and is spread in a relatively thin layer between the photo-sensitive element comprising the silver halide emulsion and the print-receiving element. The latter preferably comprises a support and a print-receiving stratum and said stratum, as noted above, includes a suitable silver precipitating layer which may constitute all or just a part of said stratum. The said stratum is separated from the support of the print-receiving element by a subcoat that is water impervious and which possesses other novel properties to be more fully described hereinafter. The Water impermeability of the subcoat is sufficient to prevent any substantial penetration of the liquid processing agent beyond the print-receiving stratum during the performance of the transfer process. In general, the process for forming the positive print takes less than five minutes for completion, and more usually only about 1 minute. It is to be understood that the term water mpermeable pertains to an impermeability to water of :his order and that said subcoat is not necessarily impervious to water vapor. As a result of this arrangement, only the print-receiving stratum of the print-receiving element is permeated to any appreciable extent by the ionic reagents contained in the liquid processing composition. The outer surface of the print-receiving stratum which contacts the layer of processing composition is preferably so constituted as to have a lesser adhesion for the solid residue of the liquid processing composition than does the photosensitive element. The entire print-receiving stratum may be essentially formed of a material having this desired stripping property. Preferably, however, a thin film of a suitable stripping composition may constitute the outer surface portion of the print-receiving stratum while the remainder of said print-receiving stratum is formed of another material more suitable for carrying the silver precipitating agents which are dispersed throughout a part at least of the thickness of said stratum. These agents function to improve the amount and character of silver precipitated during image formation. As agents, such materials as, for example, the metallic sulfides and selenides, the thiooxalates, the thioacetamides, and certain colloidal metals such as colloidal silver, gold, and mercury have been proposed. As noted above, the precipitation and aggregation of silver obtained by using the silver precipitating agents including the above-mentioned materials are very greatly improved by providing in the print-receiving stratum as a vehicle for said agents a macroscopically continuous matrix consisting essentially of submacroscopic agglomerates of particles of a water-insoluble, inorganic, chemically inert, adsorbent substance. The term subrnacroscopic is herein intended to include, Within its scope, sizes generally known as submicroscopic. This matrix material preferably has a low coefficient of absorption for light as compared to silver, and the matrix formed therefrom is essentially free of protective colloid action for silver. One example of such matrix material is a layer of silica such as is formed by drying a liquid dispersion of silica aerogel available under the trade name Santocel C.

According to the present invention the subcoat for this print-receiving stratum which includes the silver precipitating layer is preferably formed of a plurality of mate- K rials which together impart to said subcoat not only said desired water impermeability but also perform the novel function of excluding from the print-receiving stratum any oils, plasticizers, or other liquids which may originate on the underside of the print-receiving element. In this connection it should be observed again that the presence of plasticizers in a position to reach the print-receiving stratum is not in itself necessarily detrimental, provided the plasticizer is incapable of penetrating entirely through the underside of the silver precipitating layer. This condition is achieved in one form of the present invention by providing as the subcoat a pair of layers of plastic, one of which is so constituted as to be incompatible and impermeable to many of the plasticizers, which can penetrate the other plastic. Similarly, the latter plastic is so constituted as to be substantially impenetrable to many of the plasticizers which might permeate the first plastic. As a result, the combination of these two layers prevents their penetration by a relatively large number of plasticizers or similarly oily substances.

Referring now to the drawing, there is illustrated in Fig. l, by way of example, one embodiment of a novel print-receiving element 19 comprehended by the present invention. In the form shown, said element comprises a support 12,.a novel subcoat 14 and a print-receiving stratum 16. Support 12 may be formed with any suitable sheet material satisfactory for serving as a base for a photographic print. It may be, for example, an uncoated or coated paper or a film of plastic such as a 4 cellulosic ester. Preferably it is formed of baryta pape which comprises a relatively inert and pure alpha paper having coated on the surface thereof a thin film comprising a mixture of gelatin and barium sulfate.

In the present invention, baryta paper is preferred over other papers which are not equipped with a surface coating comprising a plastic such as gelatin, since the gelatin layer augments the proper functioning of the novel subcoat 14. Print-receiving stratum 16 preferably comprises a silver precipitating layer having the preferred structure noted above, namely, a matrix or vehicle comprising particles of a Water-insoluble, inorganic, chemically inert, adsorbent substance such as silica, said matrix having dispersed therethrough a silver precipitating agent such as a metallic sulfide, a metallic selenide, a thiooxalate, a thioacetarnide, colloidal silver, colloidal gold, colloidal mercury or mixtures thereof. This silver precipitating layer is preferably coated directly on subcoat 14 and may have one or more over-coats applied thereto. As disclosed in the aforesaid copending application Serial No. 234,622, there may be' applied to the silver precipitating layer an abrasion-resistant coating and, on top of this, a stripping layer.

In the form shown, novel subcoat 14 preferably comprises two superposed films 14a and 141; formed of dif ferent high molecular weight polymers, i. e., plastics. Preferably, layer 14a nearest the support has a thickness of the order of .0004 inch and is formed of a cellulosic ester, such as cellulose acetate, which is free of plasticizer.

Film 14b is preferably a polyvinyl acetal such as polyvinyl butyral or an acrylic resin such as Acryloid and in a preferred form has a thickness of the order .00015 inch. The plastic of film 14b may contain a plasticizer such as dioctyl phthalate, the methyl ester of resin sold as Abalyn, the hydrogenated rosin sold as Abytal, or the hydrogenated methyl ester of rosin sold as Hercolyn, the latter being types of plasticizers which are incompatible with cellulose acetate and therefore not capable of permeating through film 14a.

To apply film 14a a suitable solvent for cellulose acetate, such as a mixture of ethyl acetate and ethanol in an approximate ratio of 8 parts to 2 parts by weight, may be used. To apply film 14b it is important to employ as a solvent for the plastic a material in which the plastic of layer 14a is insoluble. Where layer 14a is cellulose acetate, a mixture of isopropyl acetate and methanol in the approximate ratio of 3 parts to 1 part by weight satisfies these requirements for polyvinyl butyral.

The novel print-receiving element may comprise a part of a composite film unit. A simplified and somewhat diagrammatic illustration of such film unit is shown in Fig. 2 as comprising a photosensitive element 18 which includes a fihn support or base layer 22 carrying on one surface thereof a silver halide photosensitive emulsion 20. Print-receiving element 10 is superposed on said photosensitive emulsion and there is positioned between said photosensitive layer and said print-receiving element a container 24 which carries a liquid processing composition and is capable of discharging its liquid content in a thin uniform layer between said print-receiving element and said photosensitive emulsion. Preferably, there is included in container 24 a viscous, aqueous, alkaline solution of a silver halide developer and a silver halide solvent.

The support 22 for the photosensitive emulsion 20 may be transparent so that the exposure can take place through said support, in which case the photosensitive layer and the print-receiving element may be intheir superposed relation during this exposure. Support 22 may also be opaque, in which case the photosensitive element is hingedly or otherwise secured to the printreceiving element so that it may be separated from the latterto permit exposure from the photosensitive layer side of the element. Element 18 is thereafter super" posed on the print-receiving element as shown in Fig. 2 to efiect the processing. Other film assemblies of which the novel print-receiving element may constitute a part are shown and described in my aforementioned Patent No. 2,543,181 and my Patent No. 2,579,587, issued on December 25, 1951 for Photographic Product Containing a Rupturable Container.

Since certain changes may be made in the above product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic film assembly capable of performing a ditfusion transfer reversal process and comprising a photosensitive element including a silver halide layer, a print-receiving element and a container carrying a processing liquid, said elements and said container being operatively secured together so that said container is capable of releasing its liquid content to permeate superposed portions of said elements, said print-receiving element comprising a support and a permeable printreceiving stratum, the combination with said support and said stratum of a subcoat located therebetween, said subcoat comprising two superposed films of plastic, one of said films being from the class consisting of the polyvinyl acetals and the polyacrylics, and the other of said films being a cellulosic ester.

2. A photographic film assembly as defined in claim 1 wherein said film of cellulosic ester is free of plasticizer.

3. A photographic print-receiving element for having positive prints formed thereon by means of silver transfer from a photosensitive silver halide emulsion, said print-receiving element being essentially nonphotosensitive and comprising a support, a subcoat and a thin print-receiving stratum, said print-receiving stratum comprising a silver precipitating layer coated directly on said subcoat, said silver precipitating layer being a macroscopically continuous film and consisting essentially of submacroscopic agglomerates of inert particles of a water-insoluble, inorganic substance among which a colloidal silver precipitating agent is dispersed, said particles being particles of silica, said subcoat being between said print-receiving stratum and said support and comprising two superposed films of plastic, one of said films being from the class consisting of the polyvinyl acetals and the polyacrylics, and the other of said films being a cellulosic ester.

4. A photographic print-receiving element as defined in claim 3 wherein said film of cellulosic ester is free of plasticizer.

5. A photographic print-receiving element for having positive prints formed thereon by means of silver transfer from a photosensitive silver halide emulsion, said print-receiving element being essentially nonphotosensitive and comprising a support, a subcoat and a thin print-receiving stratum, said print-receiving stratum comprising a silver precipitating layer coated directly on said subcoat, said silver precipitating layer being a macroscopically continuous film and consisting essentially of submacroscopic agglomerates of inert particles of a water-insoluble, inorganic substance among which a colloidal silver precipitating agent is dispersed, said subcoat being between said print-receiving stratum and said support and comprising two superposed films of plastic, one of said films being from the class consisting of the polyvinyl acetals and the polyacrylics, and the other of said films being a cellulosic ester.

References Cited in the file of this patent UNITED STATES PATENTS 2,216,736 Carothers Oct. 8, 1940 2,360,216 Fillius Oct. 10, 1944 2,366,723 Galley Jan. 9, 1945 2,415,631 Galley Feb. 11, 1947 2,433,515 Jahoda Dec. 30, 1947 2,462,151 Woodward Feb. 22, 1949 2,513,189 Martin June 27, 1950 2,543,181 Land Feb. 27, 1951 2,606,832 Alles et a1 Aug. 12, 1952 FOREIGN PATENTS 546,559 Great Britain July 20, 1942 568,782 Great Britain Apr. 19, 1945 687,751 Great Britain Feb. 18, 1953 59,365 Netherlands Apr. 17, 1947 

1. IN A PHOTOGRAPHIC FILM ASSEMBLY CAPABLE OF PERFORMING A DIFFUSION TRANSFER REVERSAL PROCESS AND COMPRISING A PHOTOSENSITIVE ELEMENT INCLUDING A SILVER HALIDE LAYER, A PRINT-RECEIVING ELEMENT AND A CONTAINER CARRYING A PROCESSING LIQUID, SAID ELEMENTS AND SAID CONTAINER BEING OPERATIVELY SECURED TOGETHER SO THAT SAID CONTAINER IS CAPABLE OF RELEASING ITS LIQUID CONTENT TO PERMEATE SUPERPOSED PORTIONS OF SAID ELEMENTS, SAID PRINT-RECEIVING ELEMENT COMPRISING A SUPPORT AND A PERMEABLE PRINTRECEIVING STRATUM, THE COMBINATION WITH SAID SUPPORT AND SAID STRATUM OF A SUBCOAT LOCATED THEREBETWEEN, SAID SUBCOAT COMPRISING TWO SUPERPOSED FILMS OF PLASTIC, ONE OF SAID FILMS BEING FROM THE CLASS CONSISTING OF THE POLYVINYL ACETALS AND THE POLYACRYLICS, AND THE OTHER OF SAID FILMS BEING A CELLULOSIC ESTER. 